In the field of utility construction, many electrical, sewage, gas and other utilities are buried underground. Access for such buried utilities is commonly provided by means of generally on grade access openings, usually known as manholes.
During the construction phase, after trenches have been excavated for the placement of such utilities, the generally prefabricated pipes, tunnels and casings for such utilities are installed. At various points an access opening or manhole casing will be installed in the pipe or tunnel. Of course once construction is completed the upper rim of such a manhole will preferably be at or very close to the surrounding grade, but during the construction phase the manhole casing will obviously extend several feet above the bottom of the utility trench.
This has proven to be advantageous for the purpose of ongoing survey and other work during construction, as the top of the manhole casing provides a relatively unobstructed view for alignment, leveling, etc. However, the bare rim of such a casing top provides little in the way of support for a person or persons working thereupon, even with a cover temporarily installed over the opening. Further, such a structure fails to provide the necessary means for the stabilization of any survey instruments which may be used atop the structure. Obviously, such a position atop the rim of an above grade manhole casing cover is precarious, particularly when the rim may be several feet above the surface of the base of the trench, and regulations generally prohibit or strictly control such activities.
The need arises for a safety and work platform which may be temporarily installed upon and secured to the upper rim of a prefabricated utility access opening or manhole casing during the construction of utilities and the like. The platform must be capable of being securely attached to the top of such a manhole casing or the like in order to provide safe support for one or more workers, as well as to provide a steady base for a transit or similar instrument. The platform must further meet and comply with any regulations which may govern such construction activities.